Re: [PATCH] scsi: fix uninitialized pointers with free attr

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2025-11-05 at 19:44 +0530, Ally Heev wrote:
> Uninitialized pointers with `__free` attribute can cause undefined
> behaviour as the memory assigned(randomly) to the pointer is freed
> automatically when the pointer goes out of scope
> 
> scsi doesn't have any bugs related to this as of now, but
> it is better to initialize and assign pointers with `__free` attr
> in one statement to ensure proper scope-based cleanup
> 
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes:
> https://lore.kernel.org/all/aPiG_F5EBQUjZqsl@stanley.mountain/
> Signed-off-by: Ally Heev <allyheev@gmail.com>
> ---
>  drivers/scsi/scsi_debug.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index
> b2ab97be5db3d43d5a5647968623b8db72448379..89b36d65926bdd15c0ae93a6bd2
> ea968e25c0e74 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -2961,11 +2961,11 @@ static int resp_mode_sense(struct scsi_cmnd
> *scp,
>  	int target_dev_id;
>  	int target = scp->device->id;
>  	unsigned char *ap;
> -	unsigned char *arr __free(kfree);
>  	unsigned char *cmd = scp->cmnd;
>  	bool dbd, llbaa, msense_6, is_disk, is_zbc, is_tape;
>  
> -	arr = kzalloc(SDEBUG_MAX_MSENSE_SZ, GFP_ATOMIC);
> +	unsigned char *arr __free(kfree) =
> kzalloc(SDEBUG_MAX_MSENSE_SZ, GFP_ATOMIC);
> +

Moving variable assignments inside code makes it way harder to read. 
Given that compilers will eventually detect if we do a return before
initialization, can't you have smatch do the same rather than trying to
force something like this?

Regards,

James